Functional competence of a partially engaged GPCR–β-arrestin complex

Punita Kumari,Charu Gupta,Ramanuj Banerjee,Bhagyashri Gupta,Xin Chen,Arun K Shukla,Ashish Srivastava,Deepika Jaiman,Ravi Ranjan,Pragya Gupta,Eshan Ghosh

doi:10.1038/ncomms13416

Abstract

G Protein-coupled receptors (GPCRs) constitute the largest family of cell surface receptors and drug targets. GPCR signalling and desensitization is critically regulated by β-arrestins (βarr). GPCR–βarr interaction is biphasic where the phosphorylated carboxyl terminus of GPCRs docks to the N-domain of βarr first and then seven transmembrane core of the receptor engages with βarr. It is currently unknown whether fully engaged GPCR–βarr complex is essential for functional outcomes or partially engaged complex can also be functionally competent. Here we assemble partially and fully engaged complexes of a chimeric β2V2R with βarr1, and discover that the core interaction is dispensable for receptor endocytosis, ERK MAP kinase binding and activation. Furthermore, we observe that carvedilol, a βarr biased ligand, does not promote detectable engagement between βarr1 and the receptor core. These findings uncover a previously unknown aspect of GPCR-βarr interaction and provide novel insights into GPCR signalling and regulatory paradigms.

Highlights

G Protein-coupled receptors (GPCRs) constitute the largest family of cell surface receptors and drug targets
Agonist activation results in a conformational change in GPCRs which in turn leads to heterotrimeric G protein coupling and downstream responses
It is generally believed that binding of barrs to GPCRs sterically precludes further G protein coupling leading to receptor desensitization[44,45]

Summary

Introduction

G Protein-coupled receptors (GPCRs) constitute the largest family of cell surface receptors and drug targets. GPCR–barr interaction is biphasic where the phosphorylated carboxyl terminus of GPCRs docks to the N-domain of barr first and seven transmembrane core of the receptor engages with barr. It is currently unknown whether fully engaged GPCR–barr complex is essential for functional outcomes or partially engaged complex can be functionally competent. Direct visualization of a partially engaged b2V2R–barr[1] complex[11] associated solely through the phosphorylated carboxyl terminus of the receptor by electron microscopy suggests that core interaction may be dispensable for stable assembly of the complex. We discover that a barr biased ligand does not promote core interaction between the receptor and barr

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Conclusion